The presence of petroleum oil on the surface of bodies of water is not new to the Earth's environment. For thousands of years, oil has seeped into rivers, lakes and oceans all over the world. Only in the last fifty years or so has the appearance of oil slicks on waterways been a cause for alarm.
Oil slicks on the surface of open bodies of water may result from accidental spills when a ship is being fueled; when a tanker is being loaded or unloaded; or when a tanker is wrecked and breaks up on the high seas. In some instances, oil appears on the surface of the water in rivers or ports when oil-carrying storage tanks are flushed with water. Oil slicks may also occur when leaks, fires or explosions are encountered during offshore drilling operations.
When an oil spill occurs, the oil is carried by tides, currents and winds to adjacent shore lines where it fouls beaches, kills marine animal life and plant life and adversely affects boating, bathing, fishing, or drinking water. When oil slicks develop around loading docks, ship yards, offshore drilling platforms, barges and piers, the fire potential is very serious, and in the event a slick should be ignited, the resulting fire may cause loss of life as well as property and materials. The major oil spills of recent years, wherein millions of gallons of oil have been abruptly dumped into the ocean, have magnified the need for rapid and effective means of containment.
Once an oil spill occurs, pollution damage begins immediately and is magnified many times as the oil disperses, and especially as it is washed ashore. Of the millions of dollars which are spent on the clean up of oil spills, the major part is devoted to cosmetic purposes, cleaning up the oil after the major damage has been done on shore. Dramatic savings ar available if the oil can be contained and the damage arrested at the scene of the spill.
Over the years, numerous containment methods and compositions have been tested for the removal of oil from the surface of water. In some of the prior art, absorbent materials such as sawdust, peat fibers, diatomaceous earth, expanded perlite or vermiculite, and the like, have been used to spread upon the oil slick in order to soak up the oil. For example, in U.S. Pat. No. 3,414,511, exfoliated vermiculite is floated on oil polluted water to absorb oil, which is then removed from the water by skimming the vermiculite. Similarly, in the Sinha article on "Perlite", Industrial Minerals (A. A. Balkema, Rotterdam, pp. 386-388) the author refers to the practice of port authorities to keep stocks of expanded perlite available to cope with the eventualities of oil spillage.
In other prior art, absorbents such as the above are used in combination with other reagents to clean up oil spills. For example, in U.S. Pat. No. 3,855,152 and U.S. Pat. No. 4,011,175, expanded perlite is mixed with asphalt, cellulose fibers and clay, and the resulting mixture is spread on oil spills to absorb the oil and remain floating, for subsequent collection. Along the same lines, U.S. Pat. No. 2,728,733 shows a procedure in which perlite fines are mixed with bentonite clay and fired to produce a light-weight aggregate which is scattered on the floor of machine shops to absorb water and oil.
A difficulty with materials which are mere absorbents is that they are absorbents for both water and oil, so that a large part of the absorptive capacity of the particles is consumed by saturation by water and is unavailable for pick-up of the oil. Therefore, in other prior art, efforts have been made to coat or otherwise modify the absorbents to enhance their selectivity for oil over water. Thus, for example, in U.S. Pat. No. 3,382,170, expanded perlite is coated with silicone to render it hydrophobic, and it is then used for selectively removing oil from water. In Japanese patent No. 74 45,467, perlite granules are coated with polypropylene to produce oleophilic-hydrophobic granules for the treatment of oil spills. In U.S. Pat. No. 3,696,051, vermiculite is coated with a metallic cyclopentadienyl compound and then spread on oil slicks for use as a wicking agent in enhancing the burning of the oil from the slicks. In U.S. Pat. No. 2,464,204, a mineral aggregate such as sand is mixed with petroleum asphalt and fuel oil and heated to 700 degrees F. to provide aggregate particles having a coating of solid carbon, which is then used for the treatment of oil slicks.
In view of the enormous size of the oil spills which have occurred in recent history, a need has developed for scavenging compositions which are not only selective for the petroleum oils but which have enhanced capacity for adsorbing the oil in the huge spills, as well as improved power to "lock" onto and retain the oil through the turbulent, abrasive mechanical handling conditions involved in the recovery procedure. Also, in view of the emergency nature of combating the major oil spills, there is a need for compositions which may be manufactured in readily available commercial production equipment which can be brought on-site for producing a steady flow of material for stockpile replenishment.
It is an object of the present invention to provide compositions and methods satisfying the foregoing needs.
It is another object of the invention to provide oil recovery compositions which have a durable oleophilic/hydrophobic coating which is retained through abrasive handling and stockpiling conditions and which has a substantially enhanced capacity for the adsorption of oil.
It is a further object of the invention to provide oil recovery compositions which react instantaneously with the oil and securely bind the recovered oil during the vigorous agitation that is involved in the recovery procedure.
It is still another object to provide compositions which can be manufactured in readily available equipment and which require no specialized ships or barges for dispensing at the oil spill site.
It is yet another object to provide oil recovery compositions which ca be stripped of recovered oil and recycled for the recovery of additional oil.
It is a further object to provide methods for the production and recycling of the oil recovery compositions, as well as methods for treating the oil slicks themselves.
Other object and advantages will become apparent as the specification proceeds.